Acoustical material



May 23, 1933. G. P. LITTLE 1,910,344

ACOUSTICAL MATERIAL Filed Feb. 24, 1951 Patented May 23, 1933 ism,

PATEN'F OFFICE aroma P. LITTLE, OF CHICAGO, ILLINOIS ACOUSTIGAL MATERIAL Application filed February 24, 1931. Serial No. 517,826.

This invention relates to a unitary acoustical material made from cementitious material and adapted to be used as asurfacing for walls, ceilings andthe like. A simple I but effective method of producing the acoustical bodies embraced by this invention is also described.

It has been well known that porous mate-,

rials such as for example, loosely felted boards or sheets of woven materials such as different types of cloth effectively absorb sound waves when such materials are applied as surfacing materials to interior wal s of structures, such as halls, auditoriums, dining rooms, etc. The materials of the prior art have, as a rule, been made of organic materials such as hair, vegetable fibres and the like, and are unsatisfactory as they are not fireproof. Furthermore, it has been impractical to finish these materials so as to present an artistic surface.

It has been found, for example, that if paint or other coating is applied to a loosely felted fibrous board, the paint produces a,

continuous surface on the material which substantially reduces the sound absorption characteristics of the material. Attempts have been 'made to employ porous plaster as coating material, but when such plasters are made sufiiciently porous to actually absorb soundand prevent reverberation, they are unsatisfactory because of their inherent structural weakness, difficulty of application to walls and particularly to ceilings, and by reason of the tendency for the various cavities and porosities at the surface of the coating to collect dirt.

This invention particularly relates to an making it possible to a ply the acoustical material in the form 0 units to walls'or ceiling. The difliculties'of endeavoring to obtain a porous sound absorbing cementitious layer on walls by applying a plastic cementitious material to a suitable foundation is thus obviated.

The invention also relates to a unitary sound absorbing tile capable of receiving a finished surface which can be washed, painted or otherwise treated, and in this acoustical material in unit form, thereby manner obviates the disadvanta es of the porous, dirt collecting surfaces 0 the prior art.

Inasmuch as the tile made in accordance with this invention is composed of cementitious inorganic materials, it is substantially fireproof and not subject to attack by organisms, insects, rodents and the like.

An object of this invention is to disclose and provide a unitary tile body having a smooth outer surface but having high sound absorption characteristics.

Another object is to disclose and provide a unitary cementitious tile of novel construction, said tile having enhanced sound absorption characteristics.

Another object is to disclose and provide a cementitious sound absorbing tile sub-di-' vided into? a lurality of ornamental units capable of being employed for purposes of ornamentation as well as sound absorption.

A still further object is to disclose and provide a unitary tile body comprising a structural base, a sound absorbing material carried by the base, 'and a smooth outer surface.

In describing the invention, reference will be had to the appended drawing, in which:

Fig. 1 is a plan view of one form of tile embraced by this invention.

Fig.2 is a plan view of another form of tile embraced by this invention.

Fig. 3 is a transverse section taken along the plane 3-3 indicated in Fig. 1.

Fig. 4 is a transverse section taken along the plane 4-4 in Fig. 2.

As shown in Figs. 1 and 3, the unitary tile may consist of a base member, such as the layer 10 of cementitious material. This cementitious material is preferably fairly dense and strong. If desired, reinforcing material may be embedded therein. B cementitious material as used herein, re erence may be had to various compositions containing Portland cement, gypsum, magnesium .oxy-chloride cements, and similar substances moldable in plastic form and capable of settin to form a substantially rigid and strong ody.

The base layer 10 preferably carries a plu rality of what may be called bosses, such as the bosses 11, 12 and 13, presenting a smooth outer face '14 which is rendered discontinuous by means of grooves or openings 15 separating the bosses 11, 12, 13 and the like. As shown in Fig. 1, the grooves 15 may be intersected by means of grooves 16 at right angles thereto, thereby forming the bosses 11, 12, 13 and the like. The bosses 11, 12 and 13 are preferably made of a cementitious material which may be Weaker than and preferably more porous than the base layer 10. For example, the bosses 11, 12 and 13 constituting the outer layer carried by the base member or layer 10, may be made of a gypsum composition containing diatomaceous earth, pumice, sawdust or artificially generated porosities.

Porosities of an artificial nature may be obtained by employing suitable chemicals, such as for example, sodium carbonate and an acid salt such as alum, these ingredients being added to the gypsum together with a suitable quantity of borax so as to produce a plastic cementitious mass, the sodium carbonate being dissociated and liberating carbon dioxide during the formation of the bosses 11, 12 and 13, thus producing a porous light-weight mass. The outer surface 14 is preferably troweled so as to present a smooth surface. The inner walls or opposing surfaces 17 and 18 of the grooves or openings between the individual bosses act as sound absorbing surfaces.

The depth of the grooves 15 may depend entirely upon the conditions under which it is desired to employ the tile, and normally such depth may vary from one-half to two inches. The bosses 11 and 12 may be of any 7 desired shape and size. As shown in Fig. 1, the bosses 11, 12 and 13 are square. Said squares may range in size from about one inch to six inches. The grooves 15 and 16 may vary in width (that is, the distance separating the opposedfaces l7 and 18), from about one-eighth inch to three-eighths of an'inch. a.

As shown in Figs. 2 and 4, the tile may be subdivided into a pluralit of hexagons or any other geometrical gure. When hexagonsor octa ons are employed, the outer contour of tie tile unit may follow the contour of the individual bosses formed or carried by the base. In this manner the tile may be said to be interlocking in character. As shown in Fig. 4, the layer of cementitious material 19 constituting the outer layer of the tile is attached to or carried by a fibrous wall board 20, whereas the tile shown in Figs. 1 and 3 include a base member of cementitious material 10.

Although the grooves 15 and 16 ma be readily formed in the outer layer 19 o the unitary tile body by sawing (when the bosses 11, 12, etc., are rectangular or square), I prefer to make the unitary sound absorbing tile described hereinabove in a different manner. A mould consisting of side walls, end walls and a bottom and having interior dimensions identical with the exterior dimensions of the desired tile, may be used. A grating may then be suspended in the mould box, the grating being capable of forming grooves of the desired width and thickness in the cementitious material, which is then poured into the mould box. The grating does not rest on the bottom of the mould box but is preferably spaced therefrom so as to form a backing layer or member of desired thickness. Before the cementitious material sets but after the mass has hardened, the grating may be withdrawn from the mould box leaving an article of the character shown in Figs. 1 to 4.

It is to be understood that although a particular device has been described in detail, I am not limited thereto and any suitable mould capable of being em oyed in caraying out the method described may be use After setting, the cast body may be removed from the mould and suitably dried or cured. The upper surfaces, namely, the outer surfaces 14, may be treated with a sizing material or with a hardening material. When gypsum compositions are employed for the composition from which the bosses 11', 12 and 13 are made, it has been found desirable to apply a solution of borax and alum to these surfaces so as to render them hard, thus permitting subsequent washing of these sur aces.

When tile having irregular edges are to be produced, such as forexample, a tile shown in Fig. 2, then a mould having side walls desirably deformed maybe employed, or the straight side walls 21' and 22' may carry filler blocks 28 and 29 adapted to impart the desired irregularity to the sides of the finished block.

Tile made in accordance with this invention ma be readily attached to walls, ceilings an the like by means of mortar or by first applying a rough cementitious coating to sheathing, wire lath or foundation, and then placing the pre-cast tile upon such cementitious coating while it is stillplastic. For ceiling work it may be desirable to extend suitable tie-wires through the blocks or to cast such blocks or tile with suitable hanger straps embedded therein.

Although the upper surface of the unitary acoustical tile described hereinabove is only broken by the relatively narrow and deep grooves or openings 15 and 16 which occupy but a small proportion of the total area, still it has been found that these tile prevent reverberation to a great extent and have a high absorption value, sound waves lit . composed in part of a porous cementitious material such as the composition 19, which could not be effectively applied to a wall because of its great plasticity and fluidity. The finished tile may be readily shipped or transported and when on the job may be readily sawed or cut into desired shapes or sizes to fit'corners, angles and other relatively unusual situations.

It will be understood that although I have described a particular form of acoustical material and a preferred method of making the same, I- am not to be limited to such illustrative descriptions, but this invention includes all such modifications and changes as come within the scope of the appended claims.

I claim:

1. A unitary tile body comprising a base member and a plurality of-bosses of cementitious material provided with sound absorbing porosities, said bosses being carried by said member in spaced relation to each other, said bosses being provided with opposing faces in planes transverse to the bod plane of said tile, and adapted to absorb sound.

2. A unitary tile body, comprising a cementitious base member and a plurality of bosses of porous cementitious material in spaced relation -to each other carried by said member on one side thereof, the faces of said bosses, lying in planes substantially perpendicular to the plane of the base memher, being spaced from each other sufiiciently to absorb sound waves entering said spaces between bosses.

3. A unitary sound absorbing tile body, comprising a base member, and a plurality of bosses of porous cementitious material in spaced relation to each other carried by said member, said bosses being provided with opposing faces one-half to two inches in depth and one-eighth to three-eighths inch apart .whereby said faces are adapted to absorb sound, and smooth outer faces substlantially parallel to the body plane of said ti e.

4. A unitary sound absorbing tile body, comprising a ase member, and a pluralityof bosses of cementitious material having artificially formed porosities therein, said bosses being in spaced relation to each other and extending from one surface of said base .member, said bosses being provided with opposing faces in planes parallel to the body plane of the tile and adapted to absorb sound, and smooth outer faces substantially parallel to the body plane of said tile.

5. A unitary sound absorbing tile body comprising a cementitious base member and a porous cementitious layer adhering thereto, said layer being moulded into a plurality of bosses spaced from one-eighth inch to three-eighths inch from each other whereby sound waves entering said s aces may be absorbed by the porous wal s of said bosses.

Signed at Los Angeles, Calif, this 17th day of February, 1931.

GEORGE P. LITTLE. 

